1. Field of the Invention
This invention relates to a sphygmorgh measure method and device for obtaining pulse pressure and blood flow rate simultaneously. More specifically, a device and a method placing two sets of sensors along the direction of bloodstream to measure the pulse pressures and the variations of vessel""s diameter, then use these data to calculate dynamic compliance, blood flow rate, and hemokinetics for diagnosis on physical health status.
2. Description of Prior Art
Current methods of sphygmogram rely on measuring the pressure of the pulse and the variation of the waveform, or changing the pressure into spectrums for analysis, to evaluate the health status of a person. In addition, Doppler ultrasound to measure blood flow, and measuring the velocity of red blood cell using infrared were also used. However, these methods would only obtain single data at one time period, instead of multiple signals simultaneously. Single data of pulse pressure, blood flow, or flow rate was insufficient for expressing all aspects of cardiovascular status, because the same pulse pressure may yield different blood flow due to different diameter or compliance of vessel. Furthermore, the health status and hemokinetics are closely related that the changes cannot be accurately understood by single data of pulse pressure, flow rate or flow velocity.
Suppose that the bloodstream is a laminar flow and the vessel is a linear resilient tube, a formula of blood flow rate is as follow:   Q  =            π              20        ⁢                  xe2x80x83                ⁢        α        ⁢                  xe2x80x83                ⁢        L        ⁢                  xe2x80x83                ⁢        μ              ⁡          [                                    (                                          a                0                            +                                                α                  ⁢                                      xe2x80x83                                    ⁢                                      P                    0                                    ⁢                                      xe2x80x83                                    ⁢                                      (                    t                    )                                                  2                                      )                    5                -                              (                                          a                0                            +                                                α                  ⁢                                      xe2x80x83                                    ⁢                                      P                    L                                    ⁢                                      xe2x80x83                                    ⁢                                      (                    t                    )                                                  2                                      )                    5                    ]      
Wherein:
Q is the blood flow rate;   α  =            Δ      ⁢              xe2x80x83            ⁢      a        p  
is the vessel compliance; xcex94a is the variation of the vessel diameter; and p is the pulse pressure value;
L is the distance between two measure points;
xcexc the blood viscosity coefficient;
a0 is the unstressed vessel diameter; and
PO(t) and PL(t) are the pulse pressure values of two measure points.
Therefore, the values of the vessel compliance xcex1 the blood viscosity coefficient xcexc, the vessel diameter aO, the pulse pressure values of the two measure points PO(t) and PL(t), and the distance between the two measure points L are essential to calculate the blood flow rate from the above formula. Current measure methods and devices are unable to provide simultaneously all the above data in a single process by the same device.
Theoretically, to obtain the blood flow rate in accordance with above formula, the shorter the distance between two measure points is, the more accurate the estimate of blood flow rate can be. But it will be more difficult to measure pulse pressures of two measure points when the distance is closer. According to traditional Chinese medicine, the two measure points must be within one fingertip, that is, the distance between the two measure points will be appropriate between 2 to 3 mm. Refer to FIG. 1, the pulse wave velocity (PWV) in human radial artery at wrist is about 3.5 to 4.5 m/sec, which the pulse takes approximately 0.5 millisecond to pass through these two points; and most of current-in-used sphygmorgrah devices sample the pulse pressure by frequencies from 200 to 400 Hz, i.e. a period from 20 to 50 millisecond, which obviously indicates that these devices are not able to distinguish the difference of pulse pressures at these closed points.
Besides, the difference of pulse pressure between two adjacent points is rather small, it makes difficult to convert pulse pressures from analog signal into digital signal with satisfied resolutions.
Another important factor affecting the outcome of calculation for blood flow rate is vessel compliance xcex1. A research on carotid artery shows that practical vessel compliance is non-linear which varies during arterial systole and diastole. It means that the above formula should be modified, because the vessel compliance xcex1 is no longer a constant value.
Based upon the definition of the vessel compliance, the ratio of the variation of vessel""s diameter to the pulse pressure, or the slope of a variation of vessel""s diameter and pulse pressure curve at measure point, intuitionally, it seems simply install a pressure sensor and a displacement sensor at measure point to acquire the pulse pressure signal and the variation of vessel""s diameter signal and then to calculate the nonlinear vessel compliance in a digital processing unit. But in reality, it is not applicable for noninvasive solution: at measure point, a pressure sensor should be holding stationary at certain depth against the vessel to have pressure signals; a displacement sensor should be placed to sense the variations of the vessel""s diameter. A stationary pressure sensor and a movable displacement sensor cannot be connected together to have both pressure and variations of vessel""s diameter at same measure point which results in failure of computing nonlinear vessel compliance.
As mentioned above, current methods and devices can acquire neither the values of two pulse pressures PO(t) and PL(t), nor the vessel compliance xcex1.
Accordingly, there is a need for an improved sphygmogram measure method and device, which provide solutions to the disadvantages of current counterparts.
It is therefore the objective of the present invention is to provide a sphygmogram measure method and device, which acquire pulse pressure and a blood flow rate simultaneously with the steps of:
A. Using a thermal array sensor and a thermal image identification technique to locate the artery and estimate the diameter of the vessel aO;
B. Positioning an upstream pressure sensor and a downstream pressure sensor along the direction of the bloodstream to have pulse pressure PO(t) and PL(t) respectively, detecting the time lag xcfx84 between the upstream pressure and downstream pressure, sampling analog upstream pressure signal into digital form PO(n), input PO(n) and xcfx84 to a digital signal process unit, computing the digital form of downstream pressure by PL (n)≅PL(n+xcfx84);
C. There are two methods to obtain nonlinear vessel compliance as follow.
(a) For invasive approach, placing an optical displacement sensor at the downstream measure point to measure the variation of vessel""s diameter, in the mean time, piercing a pressure sensor into the blood vessel to obtain the pulse pressure, entering these signals to a digital signal process unit and calculating the nonlinear vessel compliance xcex1(n)=xcex94a(n)/PL(n); and
(b) For noninvasive approach, a pressure feedback control method is employed. By moving upward and downward of the downstream pressure sensor to main the pressure sensor just contact the vessel and record the movement of the pressure sensor, that is, the variation of the vessel""s diameter xcex94a(n), and use the term method to have PL(n), then the nonlinear vessel compliance is computed by xcex1(n)=xcex94a(n)/PL (n);
D. Entering the blood viscosity coefficient xcexc by using viscometer or databank;
E. Computing the blood flow rate and hemokinetic energy; and
F. Extracting the biomedical features from these data and constructing a diagnosis base databank to examine the human""s health status.
Further benefits and advantages of the present invention will appear in the following descriptions and drawings.